Inertial navigation systems (INSs) are used in civil and military aviation, missiles and other projectiles, submarines and space technology as well as a number of other vehicles. An INS measures the position and attitude of a vehicle by measuring the accelerations and rotations applied to the INS's inertial frame. An INS may consist of an inertial measurement unit (IMU) combined with control mechanisms, allowing the path of a vehicle to be controlled according to the position determined by the INS. An IMU comprises a sensor assembly that contains sensitive instruments for position monitoring. The greater the accuracy of the sensitive instruments, the greater the accuracy of the position data determined by the IMU. Maintaining a nearly constant and stable temperature of the IMU improves its accuracy during calibration and flight operation, as temperature stability is directly related to sensor accuracy.
In a rotational sensor assembly supported by gas bearing pads, removing heat from the sensor assembly and controlling the temperature gradient across the sensor assembly improves the accuracy of the IMU. Uneven heat sources inside the sensor assembly cause variable temperatures on the surface of the sensor assembly. A current method of maintaining thermal stability heats the gas supplied to the gas bearing pads with a single in-line heater that supplies the entire complement of gas bearing pads. However, the slow flow rate of the gas in the gas line provides an excessive delay in thermal response and allows unspecified heat to enter or leave the system. Maintaining thermal control that accounts for changes in rotational position of the IMU would improve accuracy.